1. Field of the Invention
Modern on-highway diesel engines require the use of exhaust gas recirculation (EGR) systems. It consists of cooled exhaust gases being routed from the exhaust system (typically the turbocharger turbine inlet) to the intake manifold (usually downstream of the turbocharger compressor). EGR enables reduced combustion temperatures by diluting fresh intake air, reducing overall intake charge oxygen concentration and thereby increasing ignition delay. This, in turn, enables reduced formation of Oxides of Nitrogen (NOx), which is a result of the diesel engine combustion process. EGR flow is the result of the pressure differential between the exhaust and intake systems. A valve (poppet, check or butterfly type) is usually inserted in the EGR pipe. Controlling the EGR flow rate is critical to engine emissions control, and EGR flow control necessitates real-time knowledge of exhaust pressure. The invention described here shows an empirical method developed to estimate exhaust pressure in real-time, using a combination of three (3) two-dimensional tables. Due to the nature of exhaust gases (high temperature, high water vapor and soot content), the use of a physical pressure sensor is usually impractical, especially when put into perspective of heavy-duty diesel engine durability requirements.
The present invention relates to a method and system to operate a diesel engine using real time six dimensional empirical diesel exhaust pressure model.
The present invention further relates to a method to estimate real time exhaust pressure in an internal combustion engine to control EGR flow rate and combustion emissions.
The present invention further relates to a method and system to operate a heavy duty diesel engine to control EGR flow rates and exhaust emissions.
2. Description of the Related Art
Ramamurthy et al., U.S. Patent Application Publication 2006/0288701 is directed to a method for controlling exhaust gas particulate emission from a compression ignition engine having a variable geometry turbocharger (VGT) includes the steps of determining back pressure across the engine and air mass flow into the engine, closing the vanes of the VGT to provide air mass flow increase when backpressure is increasing, and stopping the step of closing the vanes of the VGT when a decrease in rate of change of air mass flow is determined.
Wright et al., U.S. Pat. No. 6,732,522 discloses a system for estimating the engine exhaust pressure that includes a pressure sensor fluidly coupled to an intake manifold on the engine, a turbocharger having a turbine fluidly coupled to an exhaust manifold of the engine, a control actuator responsive to a control command to control either of a swallowing capacity and a swallowing capacity of the turbine, and a control computer estimating engine exhaust pressure as a function of the pressure signal and the control command. In an alternative embodiment, the system includes an engine intake manifold and the exhaust manifold, and an EGR valve position sensor. The control computer is operable in this embodiment to estimate engine exhaust pressure as a function of the pressure signal, the control command, the engine speed signal and the EGR valve position signal.